[Xorp-users] role of pimreg interface

[Pavlin Radoslavov]

> If routerA----routerB are connected and both of them are using pimsm,
> then which will be selected as pimsm DR? Is there one pimsm DR per
> network segment? Is there an option to influence which router be the
> DR on a segment?

Yes, there is only one DR per network segment. Section 4.3.2 in the
PIM-SM spec (draft-ietf-pim-sm-v2-new-11.txt) describes the election
algorithm in details.
In summary, the router with the largest DR Priority is the DR; if
there is a tie, then the router with the larger primary IP address
is the DR.
Note that if there are legacy PIM routers that don't support the DR
Priority Hello option, then only the IP addresses are used in the
election.

In XORP you can configure the DR Priority with the
pimsm4/interface/vif/dr-priority configuration option.
See the sample rtrmgr/config.boot.sample and the XORP user manual
for details.

Pavlin